[cfe-dev] rfc: Adding a mode to -gline-tables-only to include parameter names, namespaces

[Eric Christopher]

On Wed, Apr 29, 2015 at 12:41 PM Nico Weber <thakis at chromium.org> wrote:

> On Wed, Apr 29, 2015 at 12:35 PM, Reid Kleckner <rnk at google.com> wrote:
>
>> On Wed, Apr 29, 2015 at 12:25 PM, Nico Weber <thakis at chromium.org> wrote:
>>
>>> Hi,
>>>
>>> the motivation for -gline-tables-only was to make debug info much
>>> smaller, but still include enough to get usable stack frames [1]. We
>>> recently tried using it in Chromium and discovered that the stack frames
>>> aren't all that usable: Function parameters disappear, as do function
>>> namespaces.
>>>
>>> Are there any concerns about adding a mode to -gline-tables-only (or a
>>> second flag -gline-tables-full, or similar) that includes function
>>> parameter info and namespace info but still omits most debug info?
>>>
>>> (Background: We rely on dsym files to let our crash server symbolize
>>> crash dumps we get from the wild. dsymutil uses debug info, but it
>>> apparently crashes if debug info is > 4GB. We hit that recently. So we
>>> started using -gline-tables-only, but now all our stacks are close to
>>> unusable, even though the motivation for gline-tables-only was to still
>>> have usable stacks. We can't easily use symbol names as they get stripped
>>> very early in our pipeline, and changing that is apparently involved.)
>>>
>>
>> Is there some way to change the pipeline to use the mangled name stored
>> in .symtab instead of the DW_AT_name in the DWARF? My understanding is that
>> the sanitizers already do this.
>>
>
> See "We can't easily use symbol names as they get stripped very early in
> our pipeline." above – from what I understand, one machine does the build,
> strips, runs dsymutil to get a .dSYM bundle, and then that is shipped to
> the crash servers.
>
>
(adding Greg for dsymutil issues, but I don't think there's much in the way
of solving it)
Parameter names is something we could probably add. I'd like to see the
impact of it from a size perspective. I mean, next people will want
locations of parameters. Then... and we're right back to just full debug
info.

-eric
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20150429/89b7f2df/attachment.html>